A 13-year-old with an acute change in mental status

A 13-year-old boy with Lennox-Gastaut syndrome characterized by absence, myoclonic, complex-partial, and secondarily generalized tonic-clonic seizures, presents with progressive obtundation and loss of motor and verbal skills over a 2-day period. Initial evaluation revealed therapeutic phenytoin serum concentrations. This article discusses the differential diagnosis and management approach used in this setting, as well as the appropriate interpretation of antiepileptic drug serum concentrations.